should i have it or not ?

[Ms. Golden Week]

If you are a student, or have a very tight schedule, I don't recommend having a Facebook account. They are insanely, unbelievably distracting. Maybe I'm being too hyper over here, but I know a person who got facebook and all her grades nosedived.
You don't know what you're missing out unless you start something, so it's just easier not to start facebook than trying to quit it after realizing it has become a problem in your life.

But it really depends for people. Just be smart, and try to decide if facebook is the correct choice for you. In some cases facebook can be useful for chatting people if you don't have very much free time, or even for conducting meetings and arranging clubs.
P.s. don't click on strange links in facebook. They'll give you viruses